The present invention relates to an auto-teaching technique to cause a controller for controlling movement of a transfer apparatus for a target substrate, such as a semiconductor wafer or an LCD substrate, to learn a unit of information about relative positions between the transfer apparatus itself and a holder for the target object, such as a transfer container, a process rack, or a process worktable. Where the controller has a grasp on the relative positions between the holder and the transfer apparatus in advance, it can accurately control movement of the transfer apparatus during transfer of the target substrate, such as stop positions and driving amounts of a transfer arm, and the like. The semiconductor process includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target substrate, such as a semiconductor wafer or an LCD substrate, by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target substrate.
In a vertical heat treatment system, for example, a number of semiconductor wafers are transferred by a transfer arm (or arms) from a transfer container, which is called a cassette, to a process rack, which is called a wafer boat. Then the wafers are loaded into a vertical furnace along with the wafer boat and are subjected to a heat process. In such an apparatus, it is necessary to perform a teaching operation about relative positions between the transfer arm and the cassette or the wafer boat placed at a predetermined position, after the wafer boat is washed or the transfer arm undergoes a maintenance operation.
There is a teaching method in which the transfer arm is manually controlled by an operator to perform a predetermined transfer operation, and a unit of positional information is stored in a memory on the basis of the movement of the transfer arm during the operation. However, since the wafer boat is frequently washed, it is troublesome and time-consuming to perform the manual teaching operation after the washing operation every time.
For this reason, there has been developed a technique, which is called an auto-teaching method, of automatically performing a teaching operation without relying on an operator. Jpn. Pat. Appln. KOKAI Publication No. 7-74229 discloses an auto-teaching method in which a teaching operation is performed, using a jig including a plate having a shape similar to a semiconductor wafer, and a pin vertically disposed at the center of the plate, and also using a distance-detecting sensor of a reflection type arranged on a transfer apparatus. The jig is placed on a holder, and a side surface of the jig and the pin are detected by the distance-detecting sensor, so that a unit of information about relative positions between the holder and the transfer apparatus is obtained.
This auto-teaching method, however, cannot be applied, as it is, to an existing processing system using a transfer apparatus which has no distance-detecting sensor of a reflection type and thus requires a manual teaching operation by an operator. In order to perform this method in such an existing processing system, it is necessary to provide the transfer apparatus with a distance-detecting sensor of a reflection type, thereby entailing expense, time, and labor for remodeling the processing system. Further, where a new processing system capable of performing this method is constructed, a transfer apparatus to be used therein will inevitably be complicated and expensive.